Process and apparatus for the production of seamless tubes



Aug; 17, 1937.

Filed Aug. 10, 1936 W. KNOLL v INVENTOR WERNER KNOLL BY HIS ATTORNEYS Patented Aug. .1], 1937 I UNITED STATES PROCESS AND APPARATUS FOR THE PR6- DUCTION F SEADILESS TUBES Werner Knoll, Dusseldorf-oberkassel, Germany Application August 10, 1936, Serial No. 95,250 In Germany February 26, 1935 Claims. (Ch s0 14j.

This invention is for improvements in or relating to a rolling process for the production of seamless tubes in which Pilger rolls are employed and in consequence the work is rolled out inter- 5 mittently.

The invention has for its object improvements in rolling processes employing Pilgerrolls where by improved tubes are produced having the advantages hereinafter described.

According to the invention, in a rolling process for the production of seamless tubes employing Pilger rolls, the tube is subjected during the rolling operation to a tensional force acting in the direction in which the rolls tend to. push the tube. This tensional force can, in the case of Pilger step rolling mills having stationary roll holding frames, be applied by a feed device, or in the case of Pilger step rolling mills having movable roll holding frames and oscillating or 20 rotating rolls, this force can be appliedloy the horizontal drive of the roll frames. In such a case the usual rigid coupling between horizontal ,movement of the roll frame and-rotary movement of the rolls is preferably dispensed with.

Preferably, the tensional force which is applied to the tube is regulated and this in such manner that any slip between the roll and the work is obviated. The regulation can extend over the tensional force applied during a single stroke or during the Whole rolling process, in view of the different resistances to shaping in the course of the individual stroke and of the whole rolling out process of the tube, since the wave of ma-.

terial rolled out with each stroke is a maximum 5 at the commencement of the stroke and disappears at the end.

In the course of treating the whole tube, the temperature drops and the, resistance to the change of form thereby increases. The regulation of the tensional "force is naturally therefore dependent upon the different materials to be rolled out, and upon the temperature prevailing, and furthermore upon the feed and the thickness of wall.

The process according to the invention is not restricted to the treatment of the material in the hot state, for the prdcess has also great advantages in the cold Working of tubes by Pilger rolls.

The advantage as compared with the known Pilger step rolling process resides in so controlling the conditions under which the shape of the tube is varied that during each rolling operation the so-called back bulge is avoided. This back bulging led, particularly in the production of" thin walls, to the formation of fissures or faults in the wall of the tube and prevented large reductions in cross-section. The advantage of a better variation in the shape causes also, with the cold shaping, the elimination of a harmful solidification of the structure. It is thus possible to make pieces of work, inparticular tubes, with a smoother surface and thinner wall than hitherto, in the manner given.

The invention is more particularly described, 10

byway of example, with reference to the accompanying drawing, wherein a tube 2 disposed up-.

'on a mandrel 3 is fed between Pllgerj rolls l whichare rotated in the direction of the arrows. The tube 2 is connected to the mandrel frame 15 4 by a fixing and clamping device 5, so that a tensional force can be transmitted from the feed device on to the tube.

The clamping device 5 can act on the tube from the outside or from the inside. In the ex- 20 ample shown, the clampingdevice 5 consists of two or more pivoted grippers, one end of which rests on the tube whilst the other end is regulated b-y 'an adjusting device in the form of screws. The ends ofthe grippers which make 5 contact with the tube are provided with points which penetrate into the surface of the tube in i order to increase the holding efiect thereof.

Naturally, mechanically or hydraulically actuated clamping jaws as are used in known man- 30 her on a clamping chuck, can also be employed for gripping the tube 2.

The feed of the tube to the rolls is controlled in the following manner. In a housing 6 of the feed device, there is provided in known man- 5 ner, a hydraulic brake for braking the feed movement. The brake piston l is preferably in the form of a hollow cylinder and is connected at its front end to a steeply threaded spindle M connected to the mandrel framed. I Within the 40 hollow piston l is provided a second piston t firmly connected with the housing 6 and by means of which, through the supply of a tensioning medium, such as air, steam or the like,

.the brake piston can be moved from left to 45 right and vice versa. The regulation of the tensioning medium and thus the regulation of the tensional force exerted on the tube 2 is preferably efiected under the influence of the position of the rolls l. Thus, the regulation of the ten- 50 sionalforce can be effected, for example, by a suitable regulation of the valves controlling the supply of the tensioning medium, e. g., compressed air or the like. Such a regulation of the valves can be effected, for example, by means 55 I of a cam shaft, the arrangement being such thatthe cams control the raising and lowering of the valves in accordance with the working of therolls. I The drive for the cam shaft can be derived directly from the drive for the Pilger rolls I or may be effected independently by means of a regulatable direct current motor.

.The drawing shows, by way of example, the piston l at the instant of its movement towards the rear end of the housing at the right. The tensioning medium passes through the pipe 9 into the space H .and operates to move the brake piston l to the right. This movement is tranc- 16 mitted through the spindle HI, the mandrel frame 4 and the clamping device 5 to the tube 2. Since this movement takes place whilst the rolls are' working the tube 2, the rolling process is supplemented by the tensional force thus exerted on the tube in accordance with the main feature of the invention. When the brake piston I has reached the rear dead position at the right, the rolls 1 have then released the tube 2. The valves are then suitably controlled to supply the tensioning medium to the pipe in from whence said medium passes through the axial bore i2 of the stationary piston rod 8 into the interior'of the piston 13. The piston I is thereby moved to the left and the '1 tube is again brought between the rolls I. During this counter feed movement relatively to the rolls, the tube 2 undergoes an axial rotary movement by means of the spindle l4 and a ratchet wheel I5 engaging therewith on this stroke of the piston'l. When the front dead position is reached, the rolls I again engage with the tube and the process, commences afresh.

I claim: 1. In a rolling process for the production of seamless-tubes by means of Pilger rolls, the step of subjecting the tube during the rolling operation -to a force tending to draw the tube in the direction in which the rolls tend to push the tube.

2. In apparatus forthe production of seamless tubes by rolling, the combination of Pilger rolls and a feed device for feeding a tube between said rolls, said feeding device comprising means for exerting a force on saidtube which tends to draw the tube in the direction in which said rolls tend to push said tube during the rolling operation. .5

3. In apparatus for the production of seamless tubes by rolling, the combination of Pilger rolls, a mandrel for accommodating a tube to be rolled and arranged to be drawn between said rolls, a draw rod connected at one end to said mandrel 10 and at the other end to a feeding device and a gripping device associated with the said end ofsaid draw rod to which said mandrel is connected and arranged to grip a tube to be rolled when said tube is mounted in position on the mandrel 15 and to exert on said tube a tensional force acting in the direction in which said rolls tend to push said tube during the rolling operation.

4. In apparatus for the production of seamless tubes by rolling, the combination of Pilger rolls, 20

a mandrel for accommodating a tube to be rolled and arranged to be drawn between said rolls, a draw'rod connected at one end to said mandrel and at the other end to a feeding device and an adjustable gripping device associated with the said 25 end of said draw rod to which said mandrel is connected and arranged to grip a tube to be rolled when said tube is mounted in position on the mandrel and to exert on said tube a tensional force acting in the direction in which said rolls tend to push said tube during the rolling-operation..

5. In apparatus for the production of seamless tubes by rolling, the combination of Pilger rolls, a feeding device for feeding a tube between said 85 rolls, said feeding device comprising a fluid operated piston, means for imparting to said piston a reciprocating motion and means for connecting said feeding device and tube to exert on a tube between said rolls and in one direction of move- 60 ment of said piston a tensional force which acts on said tube in the direction in which said rolls tend to push said tube during the rolling operation.

WERNER KNOLL. 

